Fluid blast circuit breaker



a; me 5 2; M1 3 Jan. 23, 1945. c. H. FLuRscHElM 2,367,934

FLUID BLAST CIRCUIT BREAKER Filed July 22, 1943 3 Sheets-Sheet 1 Inventor: Cedric H. Flurschem b5 His Attorney.

Cui mi mmm Jan. 23, 1945. c. H. FLURscHEIM FLUID BLAST CIRCUIT BREAKER Filed July 22, 1943 5 Sheets-Sheet 2 lfm/enter Ced'. "ic H. Flurschem,

b9 His Attorney.

Jan. 23. 1945. c. H. FLuRscHElM FLUID BLAST CIRCUIT BREAKER Filed July 22, 1943 3 Sheets-Sheet .'5

Inventor: Cedric, H. Flursoheim,

ls Attorney.

Patented Jan. 23, 1945 Search Roon FLUID BLAST CIRCUIT REAKER Cedric H. Flurscheim, Bowdon, England, assignor to Metropolitan-Vickers Electrical Company Limited, London, England, a company of Great Britain Application July 22, 1943, Serial No. 495,746 In Great Britain July 30, 1942 (Cl. G-148) 13 Claims.

My invention relates to fluid blast electric switches or circuit breakers of the kin-d in which the circuit is adapted to be opened by the separation of contacts within an arcing chamber to which fluid such as air or gas under pressure is supplied during the opening operation. More specically my invention is an improvement on United States Letters Patent No. 2,306,186, Rankin, assigned to the same assignee as the present application.

The interruption of a high voltage power circuit by means of a gas blast involves a number of diflicult problems due to the limited dielectric strength of gases (such as air) most commonly used. Heretofore, oil circuit breakers have been almost exclusively used for such interrupting duty since the dielectric strength of oil is many times that of air. Accordingly, when the arc .is extinguished at a current zero by the oil circuit breaker, the intervening oil dielectric is muchy better able to withstand the returning recovery voltage than air. Reestablishment of the arc therefore does not occur and the circuit remains open. Air on the other hand may be so stressed by the recovery voltage across the interrupting gap that breakdown occurs. The power arc is thlereby reignited and failure of the breaker resu ts.

It is known that the dielectric strength of a gas increases according to pressure increase; also that, in a nozzle, a back pressure in excess of 50% of the applied pressure may be permitted with no appreciable decrease in the Velocity of the gas through the nozzle. In fact, it has been established that optimum operation will theoretically be obtainable when the arrangement is such that the pressure existing on the outlet or discharge side of the nozzle of the circuit breaker is 53% of the pressure within the arcing chamber. My invention in combination makes effective use of these phenomena by separating interrupting contacts to draw an arc in a chamber in which a relatively high pressure exists, or is applied co-incident with contact separation. This arc chamber pressure does not impede the velocity or impair the effectiveness of the interrupting gas blast. An interrupter constructed in accordance with my invention is found to have the same ability to interrupt current as one using a similar but freely vented nozzle, an-d in addition is operable at much higher voltages.

It is an object of my invention to provide advantageous arrangements for controlling the pressure on the discharge side of the nozzle of a gas blast circuit breaker whereby this will be 66 maintained at a desired value without undesirable time lag, in spite of variations in the operating conditions of the circuit breaker such as may result from sudden temperature changes of the gas within the arcing chamber due to variable arcing conditions within said chamber.

It is another object of my invention to provide in an air or gas blast electric circuit breaker valve means for controlling the flow of gas on the discharge side of the gas blast nozzle with means for operating said valve means in response to both the gas pressure in the arcing chamber and the gas pressure on the discharge side of the nozzle, the pressure within the arcing chamber tending to close said valve means and the pressure on the discharge side of the nozzle tending to open said valve means whereby the opening of the valve means will be automatically adjusted to maintain the pressure on the discharge side of the nozzle in a flxed relationship to the pressure existing within the arcing chamber.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention Will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawings in which Fig. 1 is an elevational sectional view of a gas blast circuit breaker embodying the present invention with the circuit breaker in a closed position; Fig. 2 is a similar view showing the circuit breaker during an opening operation; and Figs. 3, 4, 5, 6, 7 and 8 are elevational sectional views of circuit breakers embodying modifications of my invention.

Referring now to Figs. 1 and 2 of the drawings. I have illustrated an electric circuit interrupting device comprising an arcing chamber l0 formed of a cylindrical insulating member and having slidably mounted in the upper end thereof a conducting member Il forming one contact of the circuit breaker or circuit interrupting device. The member Il includes a portion having a restricted cross-sectional area forming a nozzle I2 which Will be described in greater detail hereinafter. The member Il will be hereinafter referred to as the stationary contact of the circuit breaker although, as will become apparent from the following description, it is capable of some limited movement. The other of the relatively movable contacts of the Circuit breaker is indicated as movable contact I3 which comprises a rod-like member suitably fastened to a piston I4 slidably mounted within a cylinder I5 supported within the cylindrical arcing chamber I and arranged coaxially with the latter. Cylinder I is electrically connected to a suitable line terminal I6. The upper end of cylindrical I5 is provided with a suitable contact member I1 for insuring good electrical connection between movable contact I3 and cylinder I5, and movable contact I3 is in slidable engagement with resilient contact member I1. Movable contact I3 is biased into contacting engagement with stationary contact II by means of a compression spring I8 disposed between the under side of piston I4 and the closed lower end of cylinder I5. A suitable opening I9 is provided through piston I4 and rod contact I3 to permit air below the piston to escape during the opening operation of the circuit breaker.

When air under pressure from a suitable source (not shown) is supplied to arcing chamber I0 through conduit and valve 2| this `air or fluid will pass through openings 22 in the supporting means for cylinder I5 and through openings 23 in cylinder I5 above piston I4 to cause piston I4 to move downwardly and retract movable contact I3 from the nozzle I2 of member II which forms the so-called stationary contact. At the same time a blast of fluid from the source (not shown) will also ilow through nozzle I2 for arc extinguishing purposes. Within the nozzle portion of member I2 are suitable members 24 forming a resilient contact portion for electrically engaging movable contact I3. Member II may be suitably connected to the other line terminal, not shown.

The upper end of member II including nozzle I2 and forming the stationary cont-act of the circuit breaker is constructed of a larger diameter than the lower part thereof which lower part I I' is slidably mounted within arcing chamber I0. In order to prevent the escape of fluid between the portion II' of the member II and the arcing chamber I0 suitable sealing or gasket means, such as 25, may be provided. It will lbe Observed, therefore, that the member I I which includes the nozzle I2 and forms the stationary contact of the circuit breaker is a differential piston which is in effect provided with two piston portions, the lower one of which is subject to the air pressure within the arcing chamber I Il which pressure tends to move the member II including the constriction or nozzle I2, upwardly. The other piston portion which is of larger diameter is subject to the pressure on the discharge side of the nozzle I2 and tends to move the member I I downwardly.

The upper end of arcing chamlber I0 is preiferably provided with a hood or closure member 26 having openings 21 therein through which the uid blast from arcing chamber I0 may escape. A circumferential lip 2,8 formed on the upper piston portion of member II is adapted to engage the hood 26 when th-A pressure on the lower piston portion of member II overcomes the pressure on the upper piston portion, thereby causing member II to act as a valve controlling the discharge of air to atmosphere through the openings 21,.

The movable lmember I I comprising nozzle I2 and the stationary contact of the circuit breaker which furthermore acts as a valve means to control the discharge of the iluid blast may be light in weight so that the position of the valve means maybe caused readily to respond to variations in the pressure existing within the arcing chamber I0 which may be due to changes in the arcing conditions thereby maintaining the desired relationship between the pressure on the discharge side of the nozzle I2 and the pressure within the arcing chamber I0 without undue time lag.

The operation of the arrangement described in Figs. 1 and 2 will be obvious to those skilled in the art in view of the detailed description included above. When valve 2I is opened fluid under pressure enters cylinder I5 above piston I4 causing high speed separation between the relatively movable contacts of the circuit breaker. Withdrawal of movable contact I3 from the nozzle I2 will permit a blast of fluid to escape to atmosphere through nozzle I2 to extinguish the arc drawn between the contacts. The relative sizes of the two piston portions of the member II will cause the fluid under pressure in chamber I0 on the one hand and the nozzle discharge pressure on the other hand to position member II so that the valve opening lbetween the lip 23 and the hood 26 will provide a pressure at the discharge end of nozzle I2 which bears a predetermined relationship to the pressure existing within the arcing chamber I0. Such a positioning of member II is indicated in Fig. 2. With this arrangement the fluid blast for arc extinguishing purposes is not affected in any way and at the same time the higher dielectric strength of the fluid under presure surrounding the contacts will prevent restriking of the arc.

For circuit breakers operated on higher voltages it may be desirable to construct the nozzle member of insulating material and accordingly in Fig. 3 I have illustrated an electric circuit breaker having an arcing chamber I0 substantially like the chamber I0 of Figs. 1 and 2 except that the upper end thereof is shaped so as to provide a nozzle 30. The corresponding parts of Fig. 3 are designated lby the same reference numerals as in Figs. 1 and 2. The upper end of arcing chamber III is closed by means of a hood or cover member 3| having openings to atmosphere 32 similar to the openings 21 of Fig. 1. The stationary contact 33 of the circuit lbreaker comprises a rod depending from the center of hood 3I axially arranged Iwith respect to arcing chamber I0 and adapted to be engaged by movable contact I3. The hood 3l is also provided with a circular ilange 34 extending downwardly in coaxial arrangement with stationary contact 33 so as to form an annular cylinder. A suitable valve member 35 of insulating material is provided :with an annular portion 35 adapted to act as a piston slidably arranged within the cylinder |formed by depending ange 34. An opening 36 in the piston portion 35" is provided through which stationary contact 33 may extend. Suitable sealing means 31 may also be provided between the piston portion 35 and both the depending ange 34 and stationary contact 33. The lower portion of the valve member 35 comprises a conical portion, the outer edge of which cooperates with a circumferential lip or rim 38 formed on the upper end of arcing cham-'ber I0' above nozzle 30. The under side of the conical portion of member 35 is thus subject to the gas pressure existing at the discharge side of nozzle 30.

In order to control valve member 35 both in response to the discharge pressure of nozzle 30 and also the pressure within arcing chamber I0', I connect the cylinder formed by depending ange 34 through a suitable conduit including the insulating portion 39 with the interior of arcing chamber I. Since the piston portion 35 of member 35 subjected to the pressure of arcing chamber |0 is of considerably smaller diameter than the larger end of the conical portion of member 35 subjected to the nozzle discharge pressure, an arrangement very similar to that described in connection with Figs. l and 2 is provided, and by properly proportioning the member 35 the desired ratio between the nozzle discharge pressure and the pressure in arcing chamber I0 may be maintained at all times during the circuit interrupting operation even though the pressure within arcing chamber ||J is subject to wide variations as mentioned above.

The construction of Fig. 3 may be simplied by employing a single cylinder for both the movable contact of the circuit breaker and also for the valve member controlling the relationship between the nozzle discharge pressure and the pressure within the arcing chamber. Accordingly, in Fig. 4 I have disclosed a circuit breaker employing an arcing chamber Ill' substantially identical with the arcing chamber of Fig. S including the nozzle 3D and the circumferential lip or rim 38. In this arrangement, the stationary contact of the circuit breaker is indicated at 40 and comprises a xed rod-like member extending axially along the arcing chamber with the contact end thereof in proximity to the arcing chamber side of nozzle 30. The movable contact 4|, on the other hand, is substantially identical with rod contact |3 of Figs. l, 2 and 3 and is connected to a piston 42 reciprocally mounted in a cylinder 43 forming an extension of the hood or cover member 44 mounted on the upper end of arcing chamber I0'. A suitable compression spring 45 is provided for biasing the piston and movable contact 4| downwardly so that movable contact 4| extends through nozzle 30 into engagement with stationary contact 40. Cylinder 43 is provided with an opening 46 to permit fluid above piston 42 to escape to atmosphere during circuit interrupting operation. Stationary contact 40 which is suitably supported within arcing chamber I0' may be connected to a line terminal 41 while the other line terminal connection may be made with hood 44 which is electrically connected with movable contact 4| through a suitable sliding contact 48.

In order to cause relative separation of the contacts 40 and 4| upon introducing fluid under pressure into arcing chamber I0 cylinder 43 below piston 42 is connected with arcing chamber I0 through a suitable conduit including an insulating portion 49. As in Fig. 3, a suitable valve member 50 having an upper annular piston portion 50 is slidably mounted within a cylinder 43' being more or less an extension of the cylinder 43. This valve member is annular in form and is slldably mounted both with respect to movable contact 4| and cylinder 43'. Suitable sealing means or gaskets 5| may be pro- Y lded between valve member 50 and both rod contact 4| and cylinder 43'. Valve member 50 functions in exactly the same manner in Fig. 4 as in Fig. 3, as will be obvious to those skilled in the art.

I have found it to be desirable in certain cases to provide valve means for completely closing the discharge of the fluid or gas through the nozzle at a predetermined point during the circuit opening operation of the circuit breaker whereby after the arc drawn between the contacts has been extinguished the valve will be completely closed to prevent the flow of uid such as gas or air through the nozzle and thereby maintain the full pressure of the fluid within the arcing chamber to present the greatly increased dielectric strength. Accordingly, in Fig. 5 I have disclosed an arrangement with the corresponding parts thereof designated by the same reference numerals as in Fig. 4 in which a valve member 53 is provided similar to the valve member of Fig. 4 adapted to close completely the escape of fluid from arcing chamber Ill through nozzle 30 during the final portion of the circuit opening operation. In this arrangement the valve member 53 is provided with an additional annular ange or upwardly extending skirt 53' adapted to sealingly engage with the inner surface of hood 44' which hood is somewhat larger than the hood 44 of Fig. 4 in order to accommodate the larger valve member 53. Thus the hood 44 itself, in addition to the cylinders 43 and 43', acts as a cylinder for valve member 53 which in turn acts as a piston movable in this cylinder. If fluid under pressure is introduced into hood 44' above the upwardly extending skirt portion 53 of valve member 53 a further closing pressure will be applied to valve 53. In order that this pressure may become effective at the end of the opening stroke, I connect the cylinder formed by hood 44' to a predetermined point in cylinder 43 by means of a conduit 54. When air is supplied to arcing chamber |0' and consequently also to cylinderl 43 -below piston 42 through a conduit including the insulating portion 49, contacts 40 and 4| are separated. When piston 42 has moved upwardly a predetermined distance the end of conduit 54 connected to cylinder 43 is uncovered so that fluid under pressure is admitted into the cylinder formed by hood 44 causing the valve member 53 to close against rim 38 and maintain the pressure in the arcing chamber o-n the discharge side of nozzle 30 without any flow of air through the nozzle thereby surrounding the separated contacts with high pressure air forming a good dielectric and consequently eliminating restriking of the arc which has been extinguished. By suitably positioning the end of conduit 54 with respect to cylinder 43 the complete closing of valve 53 may be obtained at a predetermined stage during the opening operation of the circuit breaker. With a view to obtaining a desired time delay in the complete closing of the valve 53 after the initiation of the opening operation of the circuit breaker, a suitable restriction may be provided in the conduit 54 connecting cylinder 43 with the cylinder in hood 44' in which the largest diameter portion of the valve member 53 works.

The arrangement disclosed in Fig. 5 may be desirable in connection with the automatic reclosing operation of fluid or gas blast circuit breakers in which. as in the above mentioned Rankin patent, an isolating contact or switch is connected in series with the contacts of the circuit breaker and arranged so that the isolating switch is opened slightly after the opening of the contacts of the fluid blast circuit breaker. In such arrangement employing the isolating switch. the isolating switch provides the necessary ftap to prevent restriking of the arc and also to keep the circuit open when the contacts of the gas blast circuit breaker reclose after the pressure has been released from the arcing chamber, as occurs when the valve 2| in Fig. l is closed. For high speed reclosing of such circuit breakers it is desirable that the isolating switch reclose before the fluid blast contacts of the circuit breaker reclose. With the arrangement described in connection with Fig. 5 it is possible to delay the reclosure of the arcing contacts of the circuit breaker to insure that the isolating switch has reclosed. Furthermore, with the arrangement in Fig. 5 this is accomplished without the necessity of complicated control means.

It should be understood that the arrangements described heretofore may be employed in circuit breakers comprising a plurality of sets of arcing contacts with each of which a gas blast or uid blast is associated, and in such arrangements separate valve means would be employed in conjunction with each set of the contacts. In Fig. 6 I have disclosed two units of the circuit breaker of Fig. 5 mounted one upon the other in axial alignment with the cylinder housing the movable contact of the lower unit extending into the insulating arcing chamber of the upper unit and forming the stationary contact of the upper unit. The corresponding parts of Fig. 6 are designated by the same reference numerals as in Fig. 5. The only modification of the circuit breaker of Fig. 5 to produce the arrangement of Fig. 6 is a slight change in the shape of the hoods 44 which have been designated as 44l and 44" in Fig. 6. Also the arcing chamber of the upper unit designated as l must be slightly modified to permit the series arrangement of the units. The cylinder 43 of the lower unit is provided with an extension 51 which forms the stationary contact of the upper unit. A suitable opening 58 in this extension 51 is provided which functions exactly like the opening 46 of Figs. 4 and 5. Air pressure is supplied from the arcing chamber l0 of the lower unit to the arcing chamber lll of the upper unit through a suitable conduit including an insulating portion 59.

It has been found desirable, particularly in connection with gas blast circuit breakers, to complete a circuit in parallel with the interrupting contacts through a high resistance and then to interrupt the circuit through the high resistance, which is more readily accomplished than interrupting the high current initially flowing through the main current carrying contacts of the switches. This feature may be employed to advantage in connection with my invention along the lines of the arrangement disclosed in Fig. 6 in which instead of the upper unit of Fig. 6 there is provided (in Fig. 7) a hood 50 having depending therefrom a rod-like electrode 60' spaced from stationary contact 51. The lower unit of Fig. '1 is generally similar to the arrangement disclosed in Fig. with the corresponding parts thereof designated by the same reference numerals. The hood 44' is provided with suitable line terminal connections 6| while the stationary contact 40 is connected to the line terminal 41. 'Ihe electrode or stationary contact 51 extends into a suitable arcing chamber 62 upon Awhich is mounted the hood 60 supporting the electrode 60 which extends downwardly and coaxially with respect to arcing chamber 62. Arcing chamber 62 is also provided with a nozzle 63 and the openings to atmosphere 64. The predetermined point in cylinder 43 at which the conduit 54 of Fig. 6 is connected is in Fig. 7 also connected with the arcing chamber 62 through a conduit 54'. The hood or cover 60 of arcing chamber 62 is electrically connected with the lower line terminal 41 through a high resistance 65. Upon a circuit opening operation of the arrangement disclosed in Fig. 7 an arc is drawn between relatively movable contacts 40 and 4I which is extinguished rapidly, after which the valve member 53 is closed. The spacing of the electrodes 51 and 60 is such that in the absence of any fluid blast through nozzle 63 the high voltage appearing across contacts 4l and 42 upon interruption of the circuit therethrough will cause an arc to form across these electrodes and current to ow through resistance 65. As soon as the piston 42 has moved upwardly to uncover the end of conduit 54 a blast of fluid under pressure is admited to arcing chamber 62 which flowing through nozzle 63 extinguishes the arc between electrodes 51 and 60'. Because of the high resistance 65 limiting the current which can flow this extinguishing action is accomplished readily.

If desired, the electrode of Fig. I may be constructed as a movable contact 66 as shown in Fig. 8, which is carried by a piston 61 slidably mounted in a cylinder 68. With this arrangement the parallel circuit through resistor is always completed and upon interruption of the circuit through contacts 4| and 42 the current is transferred to contacts 51 and 66 and flows through resistor 65. In this case the conduit 54 would be provided with another branch 54" connected through an insulating conduit 69 to cylinder 68 below piston 51. As soon as a predetermined opening movement of contact 4I has occurred fluid under pressure is admitted to cylinder 68 below cylinder 61 to cause separation of contacts 66 and 51. If desired, a valve member 10 substantially identical to the valve member 5l) of Fig. 4 may be provided to maintain a. predetermined pressure on the discharge side of nozzle 63 formed at the end of arcing chamber 62 of Fig. 8 so as to provide a better dielectric around the contacts 51 and 66. It will be obvious that the valve 10 of Fig. 8 might take the form of` the Valve 53 of Fig. 5 so as to be completely closed when the arc between contacts 51 and 66 is extinguished. The operation of the arrangement disclosed in Figs. 7 and 8 will be obvious from the detailed description included above.

While I have illustrated specific embodiments of my invention it should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high voltage electric circuit breaker of the fluid blast type comprising relatively movable contacts, an arc extinguishing chamber having a restricted cross-sectional area at which said contacts are separable to form an arc gap, a source of fluid presfure for supplying to said chamber at one side of said restriction an arc extinguishing fluid inder pressure so that the arc in said restriction is traversed by a uid blast, and means responsive to the ratio of the fluid pressure on the exhaust side of said restriction to the fluid pressure in said chamber for maintaining the fluid pressure surrounding said contacts sufficiently high to prevent breakdown of said gap after arc interruption without adversely affecting the arc extinguishing action of the blast within said chamber.

2. A high voltage electric circuit breaker of the gas blast type comprising relatively movable conil noem MAKERS it BRAKLRS, bearb tacts, an arc extinguishing chamber having a restricted cross-sectional area at which said contacts are separable to form an arc gap, a source of gas pressure for supplying to said chamber at to the gas pressure on the exhaust side of said restriction for causing said valve member to increase the flow of said arc extinguishing gas through said restriction, means responsive to the one side of said restriction an arc extinguishing 5 gas pressure in said chamber for causing said gas under pressure so that the arc in said restricvalve member to decrease the iiow of said arc tion is traversed by a gas blast, and a differential extinguishing gas through said restriction so as piston means responsive to the ratio of the gas to maintain substantially constant the ratio of pressure on the exhaust side of said restriction the gas pressure On the exhaust Side 0f Said reto the gas pressure in sai-d chamber for maintainl0 striction to the pressure in said chamber thereby ing the gas pressure surrounding said contacts maintaining the gas pressure SilIIOuhding Said suciently high to prevent breakdown of said contacts Sllfcently high t0 prevent breakdown gap after arc interruption without adversely afof said gap after arc interruption adversely withfecting the arc extinguishing action of the blast out affecting the are extinguishing action of the Within Said Chairmen 15 blast within said chamber, and means for causing 3. A high voltage electric circuit breaker of said valve member to stop the flow 0f gas through the gas blast type comprising relatively movable said restriction upon a predetermined relative contacts, an arc extinguishing chamber having a separatiOh 0f said COIitaCtS- restricted cross-sectional area at which said con- 6. A high voltage electric circuit breaker of the tacts are separable to form an arc gap, a source fluid blast type comprising relatively movable of gas pressure for supplying to said chamber at contacts, an arc extinguishing chamber having a one side of said restriction an arc extinguishing restricted cross-sectional area at which said congas under pressure so that the arc in said restrictacts are separable to form an arc gap, a source tion is traversed by a gas blast, means for conof fluid pressure fOI Supplying t0 Said Chamber at trolling the flow of gas through said restriction 23 one side of said restriction an arc extinguishing comprising a valve member, means responsive to fluid under pressure so that the arc in said rethe gas pressure on the exhaust side of said restriction is traversed by a fluid blast, means restriction for causing said valve member to insponsive to the ratio of the uid pressure on the crease the flow of said arc extinguishing gas exhaust side of said restriction to the fluid presthrough said restriction, and means responsive gm sure in said chamber for maintaining the fluid to the gas pressure in said chamber for causing pressure surrounding said contacts suflciently said valve member to decrease the iiow of said high to prevent breakdown of said gap after arc arc extinguishing gas through said restriction interruption without adversely affecting the arc so as to maintain substantially constant the ratio extinguishing action of the blast within said of the gas pressure on the exhaust side of said chamber, and means for causing said last menrestriction to the pressure in said chamber there tioned means to stop the flow of uid through by maintaining the gas pressure surrounding said said restriction upon a predetermined relative contacts suiiiciently high to prevent breakdown separation of said contacts. of said gap after arc interruption without ad- 7. A high voltage electric circuit breaker of versely affecting the arc extinguishing action of the gas blast type comprising relatively movable the blast Within said Chamber. contacts, an arc extinguishing chamber having 4. A high Voltage electric circuit breaker of the a restricted cross-sectional area at which said gas blast type comprising relatively movable concontacts are separable to form an arc gap, a tacts, an arc extinguishing chamber having a resource of gas pressure for supplying to said chamstrictecl cross-sectional area at which said conber at one side of said restriction an arc extintacts are separable to form an arc gap, a source guishing gas under pressure so that the arc in of gas pressure for supplying to said chamber at said restriction is traversed by a gas blast, a difone side of said restriction an arc extinguishing ferential piston means responsive to the ratio of gas under pressure so that the arc in said restricthe gas pressure on the exhaust side of said retion is traversed by a gas blast, means for constriction to the gas pressure in said chamber for trolling the now of gas through said restriction maintaining the gas pressure surrounding said comprising a valve member, means responsive to contacts sufficiently high to preventl breakdown the gas pressure on the exhaust side of said reof said gas after arc interruption without acl- .striction for causing said valve member to inversely affecting the arc extinguishing action ot crease the flow of said arc extinguishing gas the blast within said chamber, and means for through said restriction, and means responsive causing said last mentioned means to stop the ilow to the gas pressure in said chamber for causing of gas through said restriction upon a predetersaid valve member to decrease the flow of said arc mined relative separation of said contacts. extinguishing gas thrOilgh said restrictin s0 as 8. A fluid blast circuit breaker for high voltage to maintain substantially constant the diiierenpower circuits comprising relatively movable contial pressure between the gas 0n the exhaust side tacts separable to form an arc gap therebetween, of said restriction and the gas in said chamber means for directing an interrupting blast of iluid regardless of changes in pressure in said chamber adjacent said arc gap for extinguishing the arc caused by said arc or the like. drawn between said contacts, a circuit including 5. A high V01tage electric Cireult breaker 0f the e5 a resistance arranged to be connected in shunt eas blast type comprising relatively movable conwith said arc gap, means including relatively septacts, an arc extinguishing Chamber having a rearable electrodes adapted to provide an auxilstricted cross-Sectional area at which Said coniary are gap serially arranged in said circuit with tacts are separable to form an are gap, a source said resistance and arranged so that the high of gas pressure for supplying to said chamber at transient voltage following extinguishment of the one side of said restriction an arc extinguishing arc drawn between said relatively movable congas under pressure so that the arc in said restrictacts will cause an arc to be drawn across said tion is traversed by a gas blast, means for conauxiliary gap and cause current to ow through trolling the iiow of gas through said restriction said resistance, and means responsive to a precomprising a valve member, means responsive 'Il determined separation of said contacts for pro..

ducing a. blast of fluid adjacent said auxiliary arc gap to interrupt the current owing through said circuit including said resistance.

9. A fluid blast circuit breaker for high voltage power circuits comprising relatively movable contacts separable to form an arc gap therebetween, means for directing an interrupting blast of fluid adjacent said arc gap for extinguishing the arc drawn between said contacts, a circuit including a resistance arranged' to be connected in shunt with said arc gap, means adapted to provide an auxiliary arc gap serially arranged in said circuit with said resistance and arranged so that the high transient voltage following extinguishment of the arc drawn between said relatively movable i contacts will cause an arc to be produced across said auxiliary gap and cause current to ow through said resistance, and means responsive to a predetermined separation of said contacts for producing a blast of fluid adjacent said auxiliary arc gap to interrupt the current flowing through said circuit including said resistance.

10. A high voltage electric circuit breaker of the fluid blast type comprising relatively movable contacts, an are extinguishing chamber having a restricted cross-sectional area at which said contacts are separable to form an arc gap, a source of fluid pressure for supplying to said chamber at one side of said restriction an arc extinguishing fluid under pressure so that the arc in said restriction is traversed by a fluid blast, means responsive to the ratio of the fluid pressure on the exhaust side of said restriction to the fluid pressure in said chamber for maintaining the fluid pressure surrounding said contacts sufiiciently high to prevent breakdown of said gap after arc interruption without affecting the arc extinguishing action of the blast withinl said chamber, and means for causing said last mentioned means to stop the ow of fluid through said restriction after a predetermined time delay upon a predetermined relative separation of said contacts.

11. A high voltage electric circuit breaker of the gas blast type comprising relatively movable contacts one of which is biased toward the closed circuit position, an operating piston connected t said biased contact, an arc extinguishing chamber having a restricted cross-sectional area in which said contacts are separable to form an arc gap, a source of gas pressure for supplying to said operating piston and to said chamber at one side of said restriction an arc extinguishing gas under pressure, said piston and biased contacts being at the exhaust side of said restriction, and valve means responsive to the ratio of the pressure on the exhaust side of said restriction to the pressure within said arc extinguishing chamber for controlling the flow of gas through said restriction.

12. A high voltage electric circuit breaker of the gas blast type comprising relatively movable contacts one of which is biased toward the closed circuit position, an operating piston connected to said biased contact, an arc extinguishing chamber having a restricted cross-sectional area. in which said contacts are separable to form an arc gap, a source of gas pressure for supplying to said operating piston and to said chamber at one side of said restriction an arc extinguishing gas under pressure, said piston and biased contacts being at the exhaust side of said restrictionI valve means responsive to the ratio of the pressure on the exhaust side of said restriction to the pressure within said arc extinguishing chamber for controlling the now of gas through said restriction, and means responsive to a predetermined separation of said contacts for causing said valve means to prevent further ow of gas through said restriction thereby surrounding the separated contacts with gas under pressure to improve the dielectric strength of the medium surrounding said contacts and prevent restriking of the arc across said contacts.

13. A high voltage electric circuit breaker of the gas blast type comprising relatively movable contacts, an arc extinguishing chamber having a restricted cross-sectional area at which said contacts are separable to form an arc gap, a source of gas pressure for supplying to said chamber at one side of said restriction an arc extinguishing gas under pressure so that the arc in said restriction is traversed by a gas blast, means for controlling the flow of gas through said restriction comprising a valve member, means responsive to the gas pressure on the exhaust side of said restriction for causing said valve member to increase the flow of said arc extinguishing gas through said restriction, mean responsive to the gas pressure in said chamber for causing said valve member to decrease the ow of said arc extinguishing gas through said restriction so as to maintain substantially constant the ratio of thc gas pressure on the exhaust side of said restriction to the pressure in said chamber thereby maintaining the gas pressure surrounding said contacts sufliciently high to prevent breakdown of said gap after arc interruption without adversely affecting the arc extinguishing action of the blast within said chamber, and means to further materially reduce the flow of gas through said restriction upon a predetermined relative separation of said contacts.

CEDRIC H. FLURSCHEIM. 

